A surge protection circuit includes a dc trigger circuit that generates a trigger signal when a surge pulse occurs, and a surge protection device, coupled to the dc trigger circuit, that generates a clamp voltage as an output voltage of the surge protection circuit and conducts surge currents to ground in response to the trigger signal. A feedback circuit is provided between the surge protection device and the dc trigger circuit. The feedback circuit lowers the clamp voltage so that it does not exceed a failure voltage of the surge protection device.
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1. A surge protection circuit, comprising:
a dc trigger circuit connected between a surge voltage node and ground, wherein the dc trigger circuit generates a trigger signal when a surge pulse occurs;
a surge protection device coupled between the surge voltage node and ground, and coupled to the dc trigger circuit for receiving the trigger signal at a control input, wherein the surge protection device generates a clamp voltage and conducts surge currents to ground in response to the trigger signal; and
a feedback circuit connected between the control input of the surge protection device and the dc trigger circuit, wherein the feedback circuit lowers the clamp voltage generated by the surge protection device;
wherein the surge protection device comprises a transistor and the feedback circuit lowers the clamp voltage so that the clamp voltage does not exceed a failure voltage of the transistor.
20. A surge protection circuit, comprising:
a dc trigger circuit connected between a surge voltage node and ground, wherein the dc trigger circuit generates a trigger signal when a surge pulse occurs;
a surge protection device coupled between the surge voltage node and ground, and coupled to the dc trigger circuit for receiving the trigger signal, wherein the surge protection device generates a clamp voltage and conducts surge currents to ground in response to the trigger signal; and
a feedback circuit connected between the surge protection device and the dc trigger circuit, wherein the feedback circuit lowers the clamp voltage generated by the surge protection device;
wherein the dc trigger circuit comprises:
a first resistor having a first terminal connected to the surge voltage node;
a dc reference connected between a second terminal of the first resistor and ground;
a first transistor (MP1) connected between the surge voltage node and ground, and having a gate connected to a first node located between the first resistor and the dc reference; and
a second resistor connected between the first transistor and ground, wherein the trigger signal is generated at a second node located between the first transistor and the second resistor.
17. A surge protection circuit, comprising:
a dc trigger circuit connected between a surge voltage node and ground, wherein the dc trigger circuit comprises:
a first resistor having a first terminal connected to the surge voltage node;
a dc reference connected between a second terminal of the first resistor and ground, and further connected to a reference voltage generator for receiving a reference voltage therefrom;
a first transistor (MP1) connected between the surge voltage node and ground, and having a gate connected to a first node located between the first resistor and the dc reference; and
a second resistor connected between the first transistor and ground, wherein dc trigger circuit generates a trigger signal at a second node located between the first transistor and the second resistor when a surge pulse occurs;
an ac trigger circuit connected to the dc trigger circuit, wherein the ac trigger circuit comprises the first and second resistors, the first transistor, and a capacitor, wherein the capacitor is connected between the first node and ground;
a surge protection device comprising a second transistor (MN1) coupled between the surge voltage node and ground, and having a gate coupled to the dc trigger circuit for receiving the trigger signal, wherein the surge protection device generates a clamp voltage and conducts surge currents to ground in response to the trigger signal; and
a feedback circuit connected between the second resistor and the dc reference, wherein the feedback circuit lowers the clamp voltage generated by the surge protection device.
2. The surge protection circuit of
3. The surge protection device of
a first resistor having a first terminal connected to the surge voltage node;
a dc reference connected between a second terminal of the first resistor and ground;
a first transistor (MP1) connected between the surge voltage node and ground, and having a gate connected to a first node located between the first resistor and the dc reference; and
a second resistor connected between the first transistor and ground, wherein the trigger signal is generated at a second node located between the first transistor and the second resistor.
4. The surge protection circuit of
5. The surge protection circuit of
6. The surge protection circuit of
a second transistor (MN2) having a gate connected to a node between said pair of resistors; and
a third transistor (MP3) connected between the second transistor and the first node, and having a gate connected to the dc reference.
7. The surge protection circuit of
8. The surge protection circuit of
a diode having an input connected to the first node; and
a fourth transistor (MP2) connected between an output of the diode and ground, and having a gate connected to a gate of the third transistor and to the reference voltage generator.
9. The surge protection circuit of
10. The surge protection circuit of
11. The surge protection circuit of
an ac trigger circuit connected to the dc trigger circuit, wherein the ac trigger circuit comprises the first and second resistors, the first transistor, and a capacitor, wherein the capacitor is connected between the first node and ground.
12. The surge protection circuit of
13. The surge protection circuit of
a second transistor (MN2) having a gate connected to a node between said pair of resistors; and
a third transistor (MP3) connected between the second transistor and the first node, and having a gate connected to the dc reference.
14. The surge protection circuit of
a diode having an input connected to the first node; and
a fourth transistor (MP2) connected between an output of the diode and ground, and having a gate connected to a gate of the third transistor and to the reference voltage generator.
15. The surge protection circuit of
16. The surge protection circuit of
18. The surge protection circuit of
a third transistor (MN2) having a gate connected to a node between said pair of resistors; and
a fourth transistor (MP3) connected between the third transistor and the first node, and having a gate connected to the dc reference.
19. The surge protection circuit of
a diode having an input connected to the first node; and
a fifth transistor (MP2) connected between an output of the diode and ground, and having a gate connected to a gate of the fourth transistor and to the reference voltage generator.
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The present invention is directed to a protection circuit and, more particularly, to an on-chip surge protection circuit.
Current and voltage spikes (i.e., energy spikes) can damage electronic circuits. Energy spikes are fast, short duration electrical transients in voltage (voltage spikes), current (current spikes), or transferred energy (energy spikes) in an electrical circuit. Such spikes can be caused by, for example, electro-static discharge (ESD) events. An uninterrupted voltage increase that typically lasts for about 50 uSec is called a “voltage surge” rather than a spike. Since voltage spikes and surges can damage sensitive electronics, many circuits include ESD and surge protection circuitry.
However, the ESD protection device 14 is only active for a very short time (several hundreds of nanoseconds or less), which may be much less than the period of a surge event, which typically has a pulse duration of around 50 μs or longer. Thus, the conventional ESD protection circuit 10 does not adequately handle surge events.
Accordingly, it would be beneficial to have an ESD protection circuit that also can protect against surge events.
The present invention provides a surge protection circuit. The surge protection circuit comprises a DC trigger circuit that generates a trigger signal when a surge pulse occurs, and a surge protection device, coupled to the DC trigger circuit, that generates a clamp voltage and conducts surge currents to ground in response to the trigger signal. A feedback circuit is connected between the surge protection device and the DC trigger circuit. The feedback circuit lowers the clamp voltage so that it does not exceed a failure voltage of the surge protection device.
The present invention is illustrated by way of example and is not limited by embodiments thereof shown in the accompanying figures, in which like references indicate similar elements. Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale.
As illustrated in
The DC reference 26 detects the DC voltage of a surge event, and with the DC trigger circuit 22, generates Vgs for the transistor MP1, such that MN1 is triggered by MP1 and R2. The AC trigger circuit triggers the surge protection device 24 against ESD events. Here, ESD events include HBM (Human Body Model) and IEC (International Electrotechnical Commission) events per IEC standards (i.e., IEC 61000-4). The transistor MP1 amplifies the trigger signals (both AC and DC), which reduces the difference in the surge voltage (Vsurge) clamp level for different surge currents. The transistor MP1 and the second resistor R2 act as an amplification circuit, which is used to trigger the surge protection device 24 to conduct ESD and surge currents to ground and generate a clamp voltage (Vclamp) when an ESD pulse occurs.
Since the surge protection circuit 20 includes both the DC trigger circuit 22 and the AC trigger circuit, the surge protection circuit 20 can provide both surge current protection and ESD protection.
The AC and DC trigger circuits 32 and 34 generate a trigger signal when a surge pulse or an ESD event occurs. The surge protection device 36 is coupled to the AC and DC trigger circuits 32 and 34, and generates a clamp voltage and conducts surge currents to ground in response to the trigger signal. The feedback circuit 38 is connected between the surge protection device 36 and the AC and DC trigger circuits 32 and 34. The feedback circuit 38 lowers the clamp voltage so that the clamp voltage does not exceed a failure voltage. In this case, the failure voltage is the breakdown voltage of the N-type transistor MN1. For example, in one embodiment, MN1 has a breakdown voltage of 7.5 v, and the clamp voltage is 6.5 v.
As discussed with reference to
The feedback circuit 38 is connected between the second resistor R2 and the DC reference 26, and as previously discussed, the feedback circuit 38 acts to clamp the surge voltage at a lower level.
In operation, after either the AC or DC trigger circuit 32 or 34 is triggered (turned on) by a surge voltage surge voltage (Vsurge), which is a voltage that is above the maximum operating voltage, and the surge protection device 36 clamps the surge voltage to a level below the failure voltage of the surge protection device 36. The feedback circuit 38 further reduces the clamp voltage to improve the voltage head room so that the voltage head room is much lower than the failure voltage.
More specifically, when either the AC or DC trigger circuit 32 or 34 turns on in response to a surge pulse, MP1 is turned on to generate the trigger signal. For example, if the DC voltage detection circuit 34 detects a DC voltage for a surge event, then the detection circuit 34 generates Vgs for MP1, which turns on MP1. The DC voltage detection circuit 34 can be on for the length of a surge pulse. The transistor MP1 and the resistor R1 trigger the surge protection device 36 (MN1) to turn on so that MN1 generates a clamp voltage Vclamp as an output voltage Vout of the surge protection circuit 30 and conducts surge currents to ground. The transistor MN1 is kept ON until the surge event is over.
The DC reference circuit 26 comprises a forward diode D1 having an input connected to the first node N1 and an output connected to a source of a second P-type transistor MP2. The second P-type transistor MP2 has a drain connected to ground and a gate that receives the reference voltage (Vref). The feedback circuit 38 comprises a third P-type transistor MP3 and a second N-type transistor MN2. The third P-type transistor MP3 has a source connected to the first node N1, a gate connected to the gate of the second P-type transistor MP2, and a drain connected to the drain of the second N-type transistor MN2. The second N-type transistor MN2 has a source connected to ground, and a gate connected to a node between the two second resistors R2_1 and R2_2.
In this embodiment, R1, D1, MP1 and MP2 detect the surge voltage. When the surge voltage is higher than a sum of the threshold of MP1, the voltage across D1, the threshold of MP2, and the reference voltage (Vref), the branch R1, D1 and MP1 provides the bias for MP1, which turns MP1 ON, which in-turn turns ON MN1 in order to bypass the surge current and clamp the surge voltage. Meanwhile, MN2 is turned ON, then MP3 is turned ON to lower the clamp voltage.
The advantage of this structure is that, using an accurate reference voltage (Vref), the clamp voltage is more accurate and there is less PVT (process, voltage, temperature) variation. Further, with the feedback circuit 38, the clamp voltage is lower than the failure voltage. For the surge protection circuit 40, the trigger voltage may be calculated as
Vtrigger=Vref+VSG_MP2+VD1+VSG_MP1 (1)
and the clamp voltage during a surge even may be calculated as:
Vclamp=Vref+VSG_MP3+VSG_MP1 (2)
From
In the above exemplary embodiments, the AC trigger circuit is not limited to having only one amplification stage (MP1, R2), and it may include multiple amplification stages for triggering the surge protection device 36 (MN1). Further, both the DC trigger circuit and the AC trigger circuit may use the same or different amplification circuits.
The N-type transistor MN1 may be a N-type MOS device or a NPN device. It is also possible to use a P-type transistor (such as MOS device or PNP device) as the surge protection device 36. However an implementation with a P-type MOS device as the surge protecting device 36 usually is less desirable due to the lower mobility/higher resistance of the P-type MOS device.
The surge protection circuit of the present invention can handle surges from several tens of volts to more than one hundred volts in mobile application. For high voltage applications, an extended drain NMOST device can be used as the current conducting unit. In addition, the surge protection circuit of the present invention can easily be integrated with Power Management Integrated Circuits (PMICs), connector ICs, load switches and other interface chips. Further, since the surge protection circuit of the present invention includes the AC trigger circuit, it also can handle ESD events.
In the foregoing specification, the invention has been described with reference to specific examples of embodiments of the invention. It will, however, be evident that various modifications and changes may be made therein without departing from the broader spirit and scope of the invention as set forth in the appended claims.
In the claims, the words ‘comprising’, ‘including’, and ‘having’ do not exclude the presence of other elements or steps then those listed in a claim. The terms “a” or “an,” as used herein, are defined as one or more than one. Also, the use of introductory phrases such as “at least one” and “one or more” in the claims should not be construed to imply that the introduction of another claim element by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim element to inventions containing only one such element, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an.” The same holds true for the use of definite articles. Unless stated otherwise, terms such as “first” and “second” are used to arbitrarily distinguish between the elements such terms describe. Thus, these terms are not necessarily intended to indicate temporal or other prioritization of such elements. The fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage.
Qing, Jian, Duan, Xindong, Tang, Shenglan
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Executed on | Assignor | Assignee | Conveyance | Frame | Reel | Doc |
Nov 11 2016 | TANG, SHENGLAN | NXP B V | 82021529 | 043579 | /0090 | |
Nov 11 2016 | QING, JIAN | NXP B V | 82021529 | 043579 | /0090 | |
Nov 11 2016 | DUAN, XINDONG | NXP B V | 82021529 | 043579 | /0090 | |
Aug 16 2017 | NXP USA, INC. | (assignment on the face of the patent) | / |
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